1. Field of the Invention
This invention relates generally to an apparatus for the treatment and ablation of body masses, such as tumors, and more particularly, to an RF treatment system suitable for multi-modality treatment with an infusion delivery device, catheter, removable electrode, insulator sleeve and introducer, all housed in the catheter. The system maintains a selected power at an electrode what is independent of changes in current or voltage.
2. Description of the Related Art
Current open procedures for treatment of tumors are extremely disruptive and cause a great deal of damage to healthy tissue. During the surgical procedure, the physician must exercise care in not cutting the tumor in a manner that creates seeding of the tumor, resulting in metastasis. In recent years, development of products has been directed with an emphasis on minimizing the traumatic nature of traditional surgical procedures.
There has been a relatively significant amount of activity in the area of hyperthermia as a tool for treatment of tumors. It is known that elevating the temperature of tumors is helpful in the treatment and management of cancerous tissues. The mechanisms of selective cancer cell eradication by hyperthermia are not completely understood. However, four cellular effects of hyperthermia on cancerous tissue have been proposed, (i) changes in cell or nuclear membrane permeability or fluidity, (ii) cytoplasmic lysomal disintegration, causing release of digestive enzymes, (iii) protein thermal damage affecting cell respiration and the synthesis of DNA or RNA and (iv) potential excitation of immunologic systems. Treatment methods for applying heat to tumors include the use of direct contact radio-frequency (RF) applicators, microwave radiation, inductively coupled RF fields, ultrasound, and a variety of simple thermal conduction techniques.
Among the problems associated with all of these procedures is the requirement that highly localized heat be produced at depths of several centimeters beneath the surface of the body. Certain techniques have been developed with microwave radiation and ultrasound to focus energy at various desired depths. RF applications may be used at depth during surgery. However, the extent of localization is generally poor, with the result that healthy tissue may be harmed. Induction heating gives rise to poor localization of the incident energy as well. Although induction heating may be achieved by placing an antenna on the surface of the body, superficial eddy currents are generated in the immediate vicinity of the antenna, when it is driven using RF current, and unwanted surface heating occurs with little heating delivered to the underlying tissue.
Thus, non-invasive procedures for providing heat to internal tumors have had difficulties in achieving substantial specific and selective treatment.
Hyperthermia, which can be produced from an RF or microwave source, applies heat to tissue but does not exceed 45 degrees C so that normal cells survive. In thermotherapy, heat energy of greater than 45 degrees C is applied, resulting in histological damage, desiccation and the denaturization of proteins. Hyperthermia has been applied more recently for therapy of malignant tumors. In hyperthermia, it is desirable to induce a state of hyperthermia that is localized by interstitial current heating to a specific area while concurrently insuring minimum thermal damage to healthy surrounding tissue. Often, the tumor is located subcutaneously and addressing the tumor requires either surgery, endoscopic procedures or external radiation. It is difficult to externally induce hyperthermia in deep body tissue because current density is diluted due to its absorption by healthy tissue. Additionally, a portion of the RF energy is reflected at the muscle/fat and bone interfaces which adds to the problem of depositing a known quantity of energy directly on a small tumor.
Attempts to use interstitial local hyperthermia have not proven to be very successful. Results have often produced nonuniform temperatures throughout the tumor. It is believed that tumor mass reduction by hyperthermia is related to thermal dose. Thermal dose is the minimum effective temperature applied throughout the tumor mass for a defined period of time. Because blood flow is the major mechanism of heat loss for tumors being heated, and blood flow varies throughout the tumor, more even heating of tumor tissue is needed to ensure effective treatment.
The same is true for ablation of the tumor itself through the use of RF energy. Different methods have been utilized for the RF ablation of masses such as tumors. Instead of heating the tumor it is ablated through the application of energy. This process has been difficult to achieve due to a variety of factors including, (i) positioning of the RF ablation electrodes to effectively ablate all of the mass, (ii) introduction of the RF ablation electrodes to the tumor site and (iii) controlled delivery and monitoring of RF energy to achieve successful ablation without damage to non-tumor tissue.
There have been a number of different treatment methods and devices for minimally invasively treating tumors. One such example is an endoscope that produces RF hyperthermia in tumors, as disclosed in U.S. Pat. No. 4,920,978. A microwave endoscope device is described in U.S. Pat. No. 4,409,993. In U.S. Pat. No. 4,920,978, an endoscope for RF hyperthermia is disclosed.
In U.S. Pat. No. 4,763,671 (the xe2x80x9c""671 patentxe2x80x9d), a minimally invasive procedure utilizes two catheters that are inserted interstitially into the tumor. The catheter includes a hard plastic support member. Around the support member is a conductor in the form of an open mesh. A layer of insulation is secured to the conductor with adhesive beads. It covers all of the conductor except a preselected length which is not adjustable. Different size tumors can not be treated with the same electrode. A tubular sleeve is introduced into the support member and houses radioactive seeds. The device of the ""671 patent fails to provide for the introduction of a fluidic medium, such as a chemotherapeutic agent, to the tumor for improved treatment. The size of the electrode conductive surface is not variable. Additionally, the device of the ""671 patent is not capable of maintaining a preselected level of power that is independent of changes in voltage or current.
In U.S. Pat. No. 4,565,200 (the xe2x80x9c""200 patentxe2x80x9d), an electrode system is described in which a single entrance tract cannula is used to introduce an electrode into a selected body site. The device of the ""200 patent is limited in that the single entrance tract fails to provide for the introduction, and removal of a variety of inserts, including but not limited to an introducer, fluid infusion device and insulation sleeve. Additionally, the device of the ""200 patent false to provide for the maintenance selected power independent of changes in voltage or.
There is a need for an RF treatment device which provides for multi-modality treatment of selected tissue sites which includes a catheter with a single entrance tract for an RF treatment electrode, an introducer, an insulator sleeve and a fluid infusion device. It would be desirable to provide an RF treatment apparatus which maintains a selected power at the electrode independent of changes in voltage or current.
Accordingly, an object of the invention is to provide an RF treatment apparatus which has a catheter insert adapted to receive interchangeable introducers and electrodes positioned in the insert.
Another object of the invention is to provide an RF treatment apparatus which has a catheter insert with interchangeable introducers and electrodes, and resources to maintain the electrode at a selected power irrespective of changes in current or voltage.
Still a further object of the invention is to provide an RF treatment apparatus, which maintains an electrode at a selected power independent of changes in current and voltage, and operates in the bipolar mode.
Yet another object of the invention is to provide an RF treatment apparatus with a needle electrode removably positioned in a catheter lumen, with resources to maintain the electrode at a selected power irrespective of changes in current or voltage.
Another object of the invention is to provide an RF treatment apparatus which includes a removable introducer that is slidably positioned in a needle lumen, and resources are incorporated which maintain a selected power of the electrode independent of changes in current or voltage.
A further object of the invention is to provide an RF treatment apparatus which includes an infusion device, catheter and a needle electrode, both removable from the infusion device which can remain positioned in a body structure to permit the introduction of a chemotherapeutic agent directly through the infusion device, or through a separate delivery device positioned in the lumen of the infusion device.
These and other objects of the invention are achieved with an RF treatment apparatus that includes a catheter with a catheter lumen. A removable needle is positioned in the catheter lumen in a fixed relationship to the catheter. The needle electrode includes a needle lumen and a needle electrode distal end. A removable introducer is slidably positioned in the needle lumen. The introducer includes an introducer distal end. A return electrode can be included that attaches to the patient""s skin. A first sensor, which can be a thermal sensor, is positioned on a surface of the electrode or the introducer. An RF power source is coupled to the needle electrode. Associated with the RF power source, return electrode and first sensor are resources for maintaining a selected power at the electrode that is independent of changes in current or voltage.
In another embodiment of the invention, the RF treatment apparatus includes a catheter with a catheter lumen. An insert is removably positioned in the catheter lumen, in a fixed relationship to the catheter. The insert includes an insert lumen and an insert distal end. A removable electrode is positioned in the insert. It has an electrode distal end that advances out of the insert distal end and introduces RF treatment energy along a conductive surface of the electrode. A first sensor is positioned on a surface of the electrode or insert. An RF power source is coupled to the electrode. Associated with the RF power source, a return electrode and first sensor are resources that maintain a selected power at the electrode which is independent of a change in voltage or current.
In a further embodiment of the invention, the RF treatment apparatus includes an infusion device with an infusion device lumen. A catheter, including a catheter lumen, is at least partially positioned in the infusion device lumen and is removable therefrom. A removable needle electrode is positioned in the catheter lumen in a fixed relationship to the catheter. The needle electrode includes a needle lumen. An insulator, with an insulator distal end, is in a surrounding relationship to the treatment needle electrode. The insulator is slidably positioned along a longitudinal axis of the treatment needle electrode and defines a needle electrode conductive surface that begins at the insulator distal end. A first sensor is positioned on a surface of the insulator or electrode. An RF power source is coupled to the needle electrode. Resources are associated with the RF power source, a return electrode and the first sensor for maintaining a selected power at the electrode that is independent of changes in voltage or current.
With the RF treatment apparatus of the invention, an insert or treatment needle is removably attached to a catheter and positioned in the catheter lumen, or the catheter is removably attached to the infusion device and positioned in the infusion device lumen. An introducer can be slidably positioned in the insert lumen initially, to assist in the introduction of the catheter and insert into a body structure. The introducer is then removed and the treatment needle substituted in its place. Temperature readings are taken adjacent to the tissue site in the vicinity of the electrode. Resources control the amount of energy supplied to the treatment site so that RF energy is delivered at low enough power so that the tissue at the electrode is not desiccated, but sufficient enough to kill the cells of the tumor.
An electrode treatment device, consisting of catheter, insulator, and either an electrode or an introducer, is removed from an infusion device following the delivery of RF energy to the tissue site. The infusion device remains positioned adjacent to or in the tumor. This permits the continued introduction of a chemotherapeutic agent to the tumor site, or subsequently, the catheter with electrode can be reintroduced and further RF energy delivered to the tumor site.
Hardware and software, collectively xe2x80x9cresources,xe2x80x9d maintain a selected power at the electrode and include a power supply, power circuits, controller, user interface and display, a device to calculate power and impedance, current and voltage sensors and a temperature measurement device. The controller can be under microprocessor control. Imaging of the tumor, through ultrasound, CT scanning, and the like, can be utilized to first define the boundaries of the tumor mass. Images of the tumor are then imported to a display. Individual electrode needles are thereafter positioned in or surround the tumor, and RF energy is then slowly delivered to the tumor. Prior treatment planning of the tumor assists in the effective delivery of RF treatment energy. Through imaging, tissue characterization by monitoring the process, is achieved. The electrodes are used in the bipolar mode.
An electrode can be removed from the catheter and placed at a different location than the catheter to measure temperature, and deliver RF energy. Multiple electrodes are introduced through their respective catheters to tumor sites. Tumor sites are treated, through hyperthermia or ablation, selectively through the controlled delivery of RF energy.
Temperature is monitored, and through the resources, a selected level of power is maintained independent of changes in voltage or current. A variety of different devices can be positioned and removed in the catheter. These include, introducers and electrodes. The treatment device of the invention permits a wide range of tumor treatment devices to be introduced to the tumor site for multi-modality evaluation and treatment purposes. The catheter or infusion device can remain positioned at the tumor site for an extended period for later treatment of RF energy or introduction of a chemotherapeutic agent.